Among the treasures in the British Library, one of the most unexpected is a collection of autographed manuscript scores that includes Mozart's thematic catalogue of his own works. Donated in 1986, these formed part of the incredible hoard accumulated by Stefan Zweig throughout his life.

The collecting habit began early. By the age of fifteen, Zweig, the indulged second son of a wealthy family of Viennese industrialists, had decided to become a writer. Praised by Hermann Hesse for his first collection of stories, Zweig decided to broaden his literary connections by inviting the celebrated writers of the day to correspond with him. His success rate increased after he took the kindly advice of one great author and began enclosing return postage; several agreed, not only to sign letters, but to sell their manuscripts to an enterprising youth who, by the age of twenty, was leading the life of a sixty-year-old, nestled among a gathering of framed photos, poems and autographs that included - his greatest jewel - a handwritten Goethe poem.

Protected from that familiar iron rod to a young writer's back - a lack of money - Zweig chose to broaden the cosy horizons of home life and the Viennese coffee-shops with travel. Aged twenty-five, and already equipped with a reputation as one of Vienna's most interesting authors, he visited London and acquired, during long hours in the great circular reading room of the old British Library, a passion for William Blake. Advised by the writer and future politician Walter Rathenau, he visited India and America, where he astonished the porter at his New York hotel by eagerly requesting to be led to the New Jersey grave of Walt Whitman.

Oliver Matuschek's authoritative and magnificently researched biography does full justice to the combination of intelligence, industry and adept networking that helped Zweig in his rise to become a figure of international reputation, with a vast popular following. At the same time, he slyly portrays a faintly comical figure, possessed by a gnawing and unslakable desire to be on handshaking terms with the great of past and present. Few men, as Matuschek observes, would have been so thrilled as Zweig to find that he lived in the same building as the daughter of Goethe's doctor; few, returning home from America on the same boat as the dying Mahler, would have attempted - as Zweig did - to scramble over the wall of suitcases that provided the great composer with a small area of privacy. (Mahler, although weak, turned his head away from view; later, as Zweig tried to ingratiate himself with Alma's small daughter, Mahler faintly asked for him to be sent away.)

Asked to comment on his brother's long-deferred marriage to the stoical and admirably loyal Friderike, Alfred Zweig commented that it had never worked. This was harsh. True, Stefan Zweig had no sympathy with his two unliterary step-daughters; true, Friderike was rapidly taught that the most she could hope for in a promiscuous man's life was the role of 'top bunny'. ('I don't begrudge him others,' Friderike gallantly announced, before adding, less sweetly: 'nor others him.') Invited to disclose, late in life, whether the marriage had been happy, Friderike declined to answer. Asked why they had no children together, she answered, with customary opacity: 'He was no Don Juan.' You can say that again. On his wedding night, Zweig left town, but not before instructing Friderike to sort out and file his drawers of old love-letters.

Obsessive, depressive and secretive in his private life, Zweig hid behind the persona of a cherished performer. Throughout the economically volatile 1920s, his works never lost their popularity. Revered for the biographical triads in which he specialised (but which did not find an English readership), Zweig moved from platform to platform, reading from his work to audiences who never failed to buy. Occasionally, one of his chosen subjects registered a protest (Freud was infuriated to be teamed with Mesmer and Mrs Baker Eddy); but Zweig's ascent never faltered. 'Onwards and upwards,' he noted in his fiftieth year. Significantly, he added a hope that the progress would not endure for long.

In 1932, despite the steady rise of Hitler and occasional published allusions to 'the Jew Zweig', the prolific author's life of Marie Antoinette sold 50,000 copies. In 1934 an order for the withdrawal of no fewer than fifteen Zweig titles from sale was hastily rescinded, for fear of public displeasure. Nevertheless, following a random search of his home for weapons and incriminating materials, Zweig went into exile. Richard Strauss, courageously insisting that the name of his new librettist should appear on posters and programmes in 1935, was delighted by the rapturous reception at Dresden of his latest opera. Three nights later, performance of Die schweigsame Frau was banned. The composer was compelled to find himself, at speed, an Aryan substitute for Zweig.

England was Zweig's first refuge and one of Matuschek's many gems is an early BBC interview, proof that English was one language in which the multilingual author was ill at ease. Beware of Pity, his surprisingly late first full-length novel, won Zweig, at last, an English audience, while Friderike's helpful discovery, at the refugee centre in Woburn Place, of a diligent German typist named Lotte led to divorce and a second, happier marriage. (Friderike, ever loyal, remained a faithful correspondent and facilitator.)

Married in 1939, the newly weds settled at Rosemount, a terraced home in Bath, where they lived among Zweig's most treasured amulets: Beethoven's desk, a Mozart song, and - a new acquisition - the score of An die Musik. A lecture in Paris (arranged by the indefatigable Friderike) about his lost Vienna led Zweig to begin work on his wonderful, if somewhat imaginative, autobiography: The World of Yesterday.

Zweig had fallen in love with the glittering beauty of Rio de Janeiro on his first visit in 1936. In 1941, following a nervous breakdown while in New York, the decision was taken that he and Lotte would settle in Brazil. Before departure, a little ominously, he made a gift to a visiting friend of the typewriter on which he had just completed his life story.

The final decision, taken in February 1942, was possibly triggered by news of the fall of Singapore to Japan. More certainly, as Matuschek strongly indicates, Zweig was ready to complete a long-held plan to end his life. Opening the door of the couple's bedroom at the hillside villa in secluded Petrópolis, the housemaid found Zweig and Lotte dead and fully clothed. The cause of death - a joint suicide by poison - was not questioned. In a last letter to Friderike, Zweig told her that the lack of books and solitude had become oppressive, but that he was now peaceful. 'Cheer up,' he concluded, 'knowing me quiet and happy.'

Oliver Matuschek has ranged widely to provide this thoughtful, balanced and sometimes pleasingly ironic account of a writer whose name was once among the most celebrated in the world. I wish that he had found space to discuss the quality of the work, as well as the life; but his intention, to provide a detailed personal portrait of Zweig and his family, has been admirably and fully achieved.